Re: C# List problem - C# Discussion Boards

Re: Proper way to sort a List<> Custom objects

30-Aug-09 12:06

Are you sure address is a double?

for home addresses, I'd expect a string.
for enumerable addresses (as in memory addresses), I would want an integer (probably uint/int or ulong/long) which is exact and maybe can be used as an array index, not something that needs conversions from double to int all the time.

Smile | :)

Luc Pattyn

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Dwayner7930-Aug-09 15:41

Dwayner79

30-Aug-09 15:41

This is why I love codeproject.

It should be a ulong. Thanks!

*****************
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C# List problem

Charlesh330-Aug-09 9:50

Charlesh3

30-Aug-09 9:50

I'm a hardware engineer trying to make my first C# program and admittedly my rusty C is only a partial help.

I do this in my form:

public partial class Form1 : Form
{
public class CUserMem
{
public UInt32 bUsed; // supposed to be a Boolean but occupies 4 bytes
public UInt32 nCFreqHz; // Center Frequency
public UInt32 nDemIdx; // demod index: 4 or 5
public UInt32 nDemBWIdx; // normally 3 for 6 kHz
public UInt32 nVBFBWHz; // user selected filter BW (3.63 is a normal choice)
public Int32 nVBFFcHz; // frequency offset of filter
public UInt32 aTime; // long (epoch time when memory was created)
public byte version; // 0 currently
public Byte[] extDC; // 3 bytes of external downconverter info
public Byte[] rsvd; // 4 bytes reserved
public char[] desc; // memory tag
}
List <cusermem> MemoryBank = new List<cusermem>(10);

public Form1()
{
InitializeComponent();

for (i = 0; i < 100; i++)
{
CUserMem TempCUserMem = new CUserMem();
MemoryBank.Add(TempCUserMem);
}
<clip the="" rest="">

I then read a file and successfully populate MemoryBank[0] to MemoryBank[99].

Later I try to pack the data by "defragging" it. Here's the code, with the problem described in the comments:

public void PackBank(decimal BankNumber)
{
for (i = 0; i < 100; i++)
{
if (MemoryBank[i].bUsed == 0)
{
for (j = i + 1; j < 100; j++)
{
if (MemoryBank[j].bUsed == 1)
{
MemoryBank[i] = MemoryBank[j];
MemoryBank[j].bUsed = 0;

// here, both the 9th and 10th memories (elements 8 and 9) are 0 while 0 to 7 are 1
MemoryBank[i].bUsed = 1;
// here, both the 9th and 10th memories are 1 and 0-7 continue to be 1
// a test using atime instead of bUsed shows the same problem
j = 100;
}
}
}
}

}

Apparently elements 8 and 9 of the array are being viewed as copies of each other. I assume this is true for any elements, not just 8 and 9.

Since I successfully populated the list with different values for those elements when I did my file I/O, why do I have a problem later when I try to write to them?

Chuck

Luc Pattyn30-Aug-09 10:25

30-Aug-09 10:25

Hi,

this does not look good. Please use PRE tags to publish code, and then make sure the formatting and indentation get preserved. If you need to show less-than signs use the special widget for them, it will insert a "<" which will end up looking like a < so we can see your generic list, assuming that is what you are using.

Only then, I'm afraid, will you get a decent reply.

Smile | :)

Luc Pattyn

Have a look at my entry for the lean-and-mean competition; please provide comments, feedback, discussion, and don’t forget to vote for it! Thank you.

Charlesh330-Aug-09 12:37

Charlesh3

30-Aug-09 12:37

Well that means that my effort to replace the < and others with the character was a big waste of time. Oddly, it appears correct for me: the correct characters are in the posting.

The FAQ doesn't mention PRE tags so hardware types like me will just gaze blankly at those words.

But let's try again. Rather than just copying and pasting the code into the Code Project window, I've saved it as a pure text file in hopes that will help. If not, I'll await instructions.

Chuck

public class CUserMem
{
public UInt32 bUsed; // supposed to be a Boolean but occupies 4 bytes
public UInt32 nCFreqHz; // Center Frequency
public UInt32 nDemIdx; // demod index: 4 or 5
public UInt32 nDemBWIdx; // normally 3 for 6 kHz
public UInt32 nVBFBWHz; // user selected filter BW (3.63 is a normal choice)
public Int32 nVBFFcHz; // frequency offset of filter
public UInt32 aTime; // long (epoch time when memory was created)
public byte version; // 0 currently
public Byte[] extDC; // 3 bytes of external downconverter info
public Byte[] rsvd; // 4 bytes reserved
public char[] desc; // memory tag
}

List <CUserMem> MemoryBank = new List<CUserMem>(10);

public Form1()
{
InitializeComponent();

for (i = 0; i < 100; i++)
{
CUserMem TempCUserMem = new CUserMem();
MemoryBank.Add(TempCUserMem);
}

<REST OF FORM1 WAS DELETED>

public void PackBank(decimal BankNumber)
{
for (i = 0; i < 100; i++)
{
if (MemoryBank[i].bUsed == 0)
{
for (j = i + 1; j < 100; j++)
{
if (MemoryBank[j].bUsed == 1)
{
MemoryBank[i] = MemoryBank[j];
MemoryBank[j].bUsed = 0;

// here, both the 9th and 10th memories (elements 8 and 9) are 0 while 0 to 7 are 1
MemoryBank[i].bUsed = 1;
// here, both the 9th and 10th memories are 1 and 0-7 continue to be 1
// a test using atime instead of bUsed shows the same problem
j = 100;
}
}
}
}
}

Luc Pattyn30-Aug-09 12:44

30-Aug-09 12:44

The FAQ may not discuss PRE tags, the sticky message "How to get an answer to your question" does.

And I forgot to tell you, under the edit box you'll find some checkboxes, the last one when checked, will cause whatever you paste to automatically adapt (i.e. replace < bY < and other such stuff).

You could clear and re-paste your code in your previous message...

Smile | :)

Luc Pattyn

Have a look at my entry for the lean-and-mean competition; please provide comments, feedback, discussion, and don’t forget to vote for it! Thank you.

OriginalGriff30-Aug-09 21:27

OriginalGriff

30-Aug-09 21:27

Your problem is quite simple, but may take some thinking about. The reason you get the problem is because of this:

if (MemoryBank[j].bUsed == 1)
   {
   MemoryBank[i] = MemoryBank[j];
   MemoryBank[j].bUsed = 0;
   MemoryBank[i].bUsed = 1;
   }

If you try the following smaller code fragment, you will get the same result:

List<cTemp> ls = new List<cTemp>(10);
int i;
cTemp ct;
for (i = 0; i < 10; i++)
    {
    ct = new cTemp(i.ToString(), i);
    ls.Add(ct);
    }
ls[5] = ls[6];
ls[6].s = "Hello";
ls[5].i = 42;
for (i = 1; i < 10; i++)
    {
    Console.WriteLine("{0}:{1}", ls[i].s, ls[i].i);
    }

class cTemp
    {
    public string s;
    public int i;
    public cTemp(string ss, int ii)
        {
        s = ss;
        ii = i;
        }
    }

Why? Because the elements of the List are references rather than the specific variables. By assigning a different reference via the line

MemoryBank[i] = MemoryBank[j];

you are "throwing away" the previous reference to the instance of the class held in MemoryBank[i], and causing both MemoryBank[i] and MemoryBank[j] to "point" to the same instance of a CUserMem class. If you then alter the content of the instance via either reference [i] or [j] you will appear to alter both instances, because they are the same. This is difficult to describe without diagrams, but if you single step the example above through the debugger, you will see what I mean.

No trees were harmed in the sending of this message; however, a significant number of electrons were slightly inconvenienced.

This message is made of fully recyclable Zeros and Ones

Charlesh331-Aug-09 17:26

Charlesh3

31-Aug-09 17:26

Griff:

I see exactly what you mean. Knowing that I am dealing with references rather than the actual values is the key, and I would not easily have discovered this as the code "looks correct".

I'll head off to do a bit of reading and Googling for the right way to solve this.

Thanks for the lesson - I bet this will prove to be a valuable piece of information in making the jump from C to C#.

Chuck

finding .resx fallback culture thru code [modified]

OriginalGriff31-Aug-09 21:36

OriginalGriff

31-Aug-09 21:36

You are welcome!
The transition from C to C# isn't too bad once you realize that all classes are on the heap, and thus all class variables are effectively C pointers to variables without the "->" all over the place. Laugh | :laugh:

No trees were harmed in the sending of this message; however, a significant number of electrons were slightly inconvenienced.

This message is made of fully recyclable Zeros and Ones

yanairon30-Aug-09 6:00

yanairon

30-Aug-09 6:00

Hi,

I want to be able to know what is the fallback mechanism for a language, and do it in code.

for example: i have files that aren't resource files but are different for different cultures.

i want to search manualy for a culture directory according to my culture. and if i don't find it there, i want to search for the fallback culture and so on, till i get to the root directory if the culture isn't found.

My question is: how can i find the "next fallback" culture for a given culture, thru code.

Thanks,
Yanai

[SOLVED]
The CultureInfo class has a "Parent" property just for that Smile | :)

modified on Monday, August 31, 2009 7:28 AM

[Answered] Creating a list/collection containing different object types [modified]

Trollslayer30-Aug-09 5:24

Trollslayer

30-Aug-09 5:24

I am analysing data which contains several different object types and would like to get them in a single collection but need to keep them in order.
I could use a dictionary and lists of each type but it would be easier (and maybe quicker) if I could have a single collection of the objects as the order the lists are in the original data is important.
Any suggestions on a reasonable method?
Thanks.

Elaine Rose | [Rose]

Visit http://www.notreadytogiveup.com/[^] and do something special today.

modified on Sunday, August 30, 2009 12:16 PM

Re: Creating a list/collection containing different object types

PIEBALDconsult30-Aug-09 5:34

PIEBALDconsult

30-Aug-09 5:34

object[] ? ArrayList ? List<object> ?

Re: Creating a list/collection containing different object types

Trollslayer30-Aug-09 6:16

Trollslayer

30-Aug-09 6:16

Thanks PB, I'm still learning about collections.

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Re: Creating a list/collection containing different object types

Luc Pattyn30-Aug-09 6:29

Re: Creating a list/collection containing different object types

30-Aug-09 6:29

Collect items of the most specialized common type, Object[] or List<Object> would always work; if you have some intermediate base class, that would be even better. So for a drawing it could be Shape[] or List<Shape> where your shapes inherit from your base or abstract Shape class.

Smile | :)

Luc Pattyn

Have a look at my entry for the lean-and-mean competition; please provide comments, feedback, discussion, and don’t forget to vote for it! Thank you.

Trollslayer30-Aug-09 6:54

Trollslayer

30-Aug-09 6:54

A good idea, the other method would be something akin to the MFC VARIANT type where the members are the class types I need to put in the list.
I'll try your suggestion first.
Thanks Luc.

Visit http://www.notreadytogiveup.com/[^] and do something special today.

Re: Creating a list/collection containing different object types

Luc Pattyn30-Aug-09 10:26

UDP - Server (EndReceiveFrom) doesn't work

30-Aug-09 10:26

Luc Pattyn

Have a look at my entry for the lean-and-mean competition; please provide comments, feedback, discussion, and don’t forget to vote for it! Thank you.

softwarejaeger30-Aug-09 5:16

softwarejaeger

30-Aug-09 5:16

Hello,

i had a running UDP-Server, but had the problem, that only every second package coming on. So now i wanted to re-code it with Socket and not using the UdpClient.

If i want to receive a datagram with Socket.EndReceiveFrom(ar,ref ep) it doesn't works. I get a NullReferenceException (i think the "ep" is the problem), but if i use Socket.EndReceive(ar) it works well.

Here the code:

string szData;
IPEndPoint ipe = new IPEndPoint(IPAddress.Any, 0);
EndPoint ep = (EndPoint)ipe;
int len = parent.udp_listen.EndReceiveFrom(ar,ref ep);
szData = Encoding.ASCII.GetString(buffer, 0, len);

"parent.udp_listen" is the public UdpClient which is in another class.

So what's wrong... is there another possibility to find out who is the sender of the datagram? Because i need the IP Address and the sending-Port of the sender.

Thanks

Job market Aussie ???

UBX30-Aug-09 4:02

UBX

30-Aug-09 4:02

Is there a job market in Aus for C#.net asp.net ???

Just curious ...

Abhishek Sur30-Aug-09 6:29

Abhishek Sur

30-Aug-09 6:29

Is this the right section to post this ?? WTF | :WTF:

Abhishek Sur

My Latest Articles
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UBX30-Aug-09 9:08

UBX

30-Aug-09 9:08

Well, where the hell would you post it ???
Laugh | :laugh:

DaveyM6930-Aug-09 11:11

DaveyM69

30-Aug-09 11:11

Probably in the Lounge[^]

Dave
BTW, in software, hope and pray is not a viable strategy. (Luc Pattyn)
Visual Basic is not used by normal people so we're not covering it here. (Uncyclopedia)
Why are you using VB6? Do you hate yourself? (Christian Graus)

Joe Woodbury30-Aug-09 11:38

Joe Woodbury

30-Aug-09 11:38

No, to my knowledge Australia is not allowed to use .NET, let alone C#. This is why Chris Maunder moved to Canada.